I believe that we do not know anything for certain, but everything probably.

Letter to Pierre Perrault, 'Sur la préface de M. Perrault de son traité de l'Origine des fontaines' [1763], Oeuvres Complètes de Christiaan Huygens (1897), Vol. 7, 298. Quoted in Jacques Roger, The Life Sciences in Eighteenth-Century French Thought, ed. Keith R. Benson and trans. Robert Ellrich (1997)